"Do you drink juice and milk?"
Translation:Ви п'єте сік і молоко?
The apostrophe is acting like a ъ (твёрдый знак). And, no, the explanation is rather simple: it is just how Ukrainian works.
Apparently, all labial consonants (м, б, п, в, ф) almost require this "hard sign" before я, ї, є, ю (except when they are preceded by a voiced consonant inside the root; doesn't work if it is a prefix ending in a voice consonant), and р (in certain cases). There are rules that you may read up later :).
It is not marked as correct because it is incorrect. The appropriate form can bee seen in the main translation (above).
English got rid of its singular "thou", with only "you" left to work or both.